Many microcontrollers and microprocessors contain embedded memories such as ROM. Typically, it is not possible to modify the memory of embedded ROM after manufacture. In the case of Write Once Memory, it is only possible to modify the memory once.
It is standard in the industry to develop software applications for embedded processors. In order to develop and test software on real-time (or full speed) silicon it is necessary to bond out the read only memory on externally accessible bond out pads. The internal memory is isolated and replaced by external memory connected to the bond out pads.
Currently, manufacturers use bond out memory in development silicon. However, the standard approach requires that the provision of bond out pads occupy a significant amount of silicon area, resulting in a significant increase in product cost. Manufacturers have addressed this issue by either absorbing the costs or by manufacturing two variants of silicon, one for development purposes that includes bond out pads and a production version that does not include bond out pads. Both approaches lead to an increase cost of production.
Accordingly, what is desired is a cost-efficient method of manufacturing semiconductor wafers that can be used for both product and development purposes. The present invention addresses this need.